Synergistic degradation of PNP via coupling H2O2 with persulfate catalyzed by nano zero valent iron

H₂O₂ and persulfate (PDS) activated by iron are attracting much attention due to their strong oxidation capacity for the effective degradation of organic pollutants. However, they face problems such as requiring an acidic reaction pH and difficulty of Fe²⁺ regeneration. In this study, the simultaneous activation of H₂O₂ and persulfate by nanoscaled zero valent iron (nZVI) was investigated for the degradation of p-nitrophenol (PNP). The nZVI/H₂O₂/PDS oxidation system exhibited significantly higher reactivity toward PNP degradation than the systems with a single oxidant. A synergistic effect was explored between H₂O₂ and PDS during nZVI-mediated activation, and the molar ratio of H₂O₂/PDS was a key parameter in optimizing the performance of PNP degradation. The nZVI/H₂O₂/PDS system could function well in a wide pH range, and even 95% PNP was removed at an initial pH 10, thus markedly alleviating the pH limitations of Fenton-like processes. Both hydroxyl radicals and sulfate radicals could be identified during H₂O₂/PDS activation, in which H⁺ produced during PDS decomposition promoted H₂O₂ activation. The increase of oxidant concentration could significantly enhance the PNP degradation, while the presence of HCO₃⁻ and HPO₄²⁻ exerted great inhibition. Furthermore, five degradation intermediates of PNP were detected and its degradation pathways in the nZVI/H₂O₂/PDS system were presented. This study reveals that the simultaneous activation of H₂O₂ and PDS by nZVI is a promising advanced oxidation tool as an alternative to typical Fenton processes for recalcitrant pollutant removal.

Simultaneous activation of H₂O₂ and persulfate by nanoscaled Fe⁰ shows synergistic effect for degradation of p-nitrophenol with generating both hydroxyl and sulfate radicals in a wide initial pH range.     

The efficient degradation of organic pollutants in an aqueous environment under visible light irradiation by persulfate catalytically activated with kaolin-Fe2O3

In recent years, persulfate (PS) has been widely studied as a promising oxidant. In this work, a new K-Fe₂O₃ catalyst was synthesized via a facile impregnation method. K-Fe₂O₃ samples were utilized as heterogeneous photocatalysts for the degradation of aquatic organic pollutants (rhodamine, RhB, and ciprofloxacin, CIP). The catalysts showed excellent catalytic activity in the presence of PS under the irradiation of visible light, owing to the generation of SO₄˙⁻ and ·OH active radicals. The degradation ratio and COD removal ratio for RhB were 99.8% and 88.3%. More importantly, the system retained a high degradation activity for RhB within a wide operating pH range of 2.9–10. The results of cycling degradation experiments confirmed that the K-Fe₂O₃ catalyst was stable and recoverable. Large-scale experiments for treating dye wastewater under irradiation by natural sunlight were carried out, showing that this study can provide a new perspective for the treatment of wastewater.

Characterizations and properties of catalysts.     

Influence of solution pH on degradation of atrazine during UV and UV/H2O2 oxidation: kinetics,mechanism, and degradation pathways

The kinetics, degradation mechanism and degradation pathways of atrazine (ATZ) during sole-UV and UV/H₂O₂ processes under various pH conditions were investigated; the effects of UV irradiation time and H₂O₂ dose were also evaluated. A higher reaction rate was observed under neutral pH conditions in the UV only process. For the UV/H₂O₂ process, a higher reaction rate was observed in acidic solution and the degradation rate of ATZ firstly increased with the increase of concentration of H₂O₂ and then decreased when H₂O₂ concentration exceeded 5 mg L⁻¹. In addition, qualitative and quantitative analyses of oxidation intermediates of ATZ in aqueous solution during the sole-UV and UV/H₂O₂ processes were conducted using UPLC-ESI-MS/MS. Ten kinds of dechlorinated intermediates were detected during sole-UV treatment under all five pH conditions. In contrast, the speciation of intermediates in the UV/H₂O₂ process varied dramatically with solution pH. Based on the analysis of ATZ oxidation intermediates, ATZ degradation pathways under different pH conditions were proposed for the sole-UV and UV/H₂O₂ processes. The results showed that the main degradation reactions of ATZ included dechlorination-hydroxylation, dechlorination-dealkylation, de-alkylation, deamination-hydroxylation, alkylic-oxidation of lateral chains, dehydrogenation-olefination, dechlorination-hydrogenation, dechlorination-methoxylation and dehydroxylation.

The kinetics, degradation mechanism and degradation pathways of atrazine (ATZ) during sole-UV and UV/H₂O₂ processes under various pH conditions were investigated; the effects of UV irradiation time and H₂O₂ dose were also evaluated.     

Visible-light photoelectrocatalysis/H2O2 synergistic degradation of organic pollutants by a magnetic Fe3O4@SiO2@mesoporous TiO2 catalyst-loaded photoelectrode

In this paper, we describe a method for photoelectrocatalysis (PEC)/H₂O₂ synergistic degradation of organic pollutants with a magnetic Fe₃O₄@SiO₂@mesoporous TiO₂ (FST) photocatalyst-loaded electrode. At optimal conditions of pH 3.0, 2.25% H₂O₂, working electrode (fixed FST 30 mg) potential +0.6 V (vs. SCE), and 10 mg L⁻¹ of all experimental pollutants, the FST PEC/H₂O₂ synergistic system exhibited high activity and stability for the removal of various organic pollutants under visible light with comparable degradation efficiencies, including MB (98.8%), rhodamine B (Rh B, 96.7%), methyl orange (MO, 97.7%), amoxicillin (AMX, 83.9%). Moreover, this system obtained TOC removal ratios of 83.5% (MB), 77.9% (Rh B), 80.2% (MO), 65.5% (AMX) within 8 min. The kinetic rate constants of the PEC/H₂O₂ synergistic system were nearly 53 and 1436 times higher than that of the PEC process and H₂O₂ photolysis under visible light, respectively. Furthermore, the main reactive oxidant species (˙OH, ˙O₂⁻) were studied and enhanced mechanisms of the photocatalytic-electro-H₂O₂ coupling system were proposed. This work brings new insights to efficiently purify organic pollutants by PEC coupled with peroxide under solar light illumination.

A visible-light PEC/H₂O₂ synergistic system based on Fe₃O₄@SiO₂@mesoporous TiO₂ photocatalysts was constructed. Reaction mechanisms during PEC/H₂O₂ coupling system were elucidated.     

Kinetic and mechanistic investigations of the degradation of propranolol in heat activated persulfate process

This study investigated the heat activated persulfate (heat/PS) process in the degradation of propranolol from water. Various factors (e.g., temperature, persulfate dose, initial pH and natural water constituent) on PRO degradation kinetics have been investigated. The results showed that the PRO degradation followed a pseudo-first-order kinetics pattern. As temperature rises, the pseudo-first-order rate constant (k_obs) was improved significantly, and the k_obs determined at 40–70 °C satisfied the Arrhenius equation, yielding an activation energy of 99.0 kJ mol⁻¹. The radical scavenging experiments and the EPR tests revealed that both SO₄˙⁻ and ·OH participated in degrading PRO, with SO₄˙⁻ playing a dominant role. Higher PS concentration and neutral pH favored PRO degradation. The impact of Cl⁻ and HCO₃⁻ were concentration-dependent. A lower concentration of Cl⁻ and HCO₃⁻ could accelerate PRO degradation, while the presence of HA showed inhibitory effects. Seven degradation products were recognized through LC/MS/MS analysis. Cleavage of ether bond, hydroxylation, and ring-opening of naphthol moiety are involved in the PRO''s degradation pathway. Finally, the formation of disinfection byproducts (DBPs) before and after pre-treated by heat/PS was also evaluated. Compared with direct chlorination of PRO, the heat/PS pre-oxidation greatly impacted the DBPs formation. The higher PRO removal efficiency in natural water indicated the heat/PS process might be capable of treating PRO-containing water samples, however, its impacts on the downstream effect on DBPs formation should be also considered.

The degradation kinetics and mechanism of propranolol by heat activated persulfate oxidation were investigated.     

Catalytic degradation of diclofenac from aqueous solutions using peroxymonosulfate activated by magnetic MWCNTs-CoFe3O4 nanoparticles

CoFe₃O₄ nanoparticles supported on multi-walled carbon nanotubes (MWCNTs-CoFe₃O₄) were synthesized by the co-precipitation method as a novel catalyst for degradation of diclofenac (DCF). The comparative experiments indicated that MWCNTs-CoFe₃O₄ has a better catalytic activity in degradation of DCF and activation of peroxymonosulfate (PMS) compared to other catalytic systems. This can be attributed to the interaction of MWCNTs with CoFe₃O₄ in accelerating the absorption process and activating the PMS (E_a = 22.93 kJ mol⁻¹). The removal efficiencies of DCF and total organic carbon (TOC) were 99.04% and 50.11%, under optimum conditions, e.g., pH of 7, PMS dosage of 4 mM, DCF concentration of 30 mg L⁻¹, catalyst dosage of 500 mg L⁻¹, and reaction time of 120 min. The oxidation of DCF was fitted by the pseudo-first-order kinetic model and the constant rate was increased by increasing the pH, temperature, dosage of PMS and catalyst. The production of reactive species was studied using scavengers such as TBA and ethanol and the results showed that sulfate radical is the reactive species responsible for the degradation of DCF. The MWCNTs-CoFe₃O₄ catalyst showed high stability and reusability based on five successful repeated reactions, X-ray diffraction and energy dispersive X-ray spectroscopy analysis. Based on the intermediates detected by gas chromatography-mass spectrometry (GC-MS), the possible pathways for DCF catalytic oxidation were proposed. The results explained that the PMS/MWCNTs-CoFe₃O₄ system is a promising method for treating DCF solution due to high efficiency, good reusability of catalyst and greater PMS activation.

The MWCNTs-CoFe₃O₄ as a novel catalyst showed high catalytic activity in activation of proxymonosulfate for degradation of diclofenac.     

Chemically and thermally activated persulfate for theophylline degradation and application to pharmaceutical factory effluent

Degradation of PPCPs by AOPs has gained major interest in the past decade. In this work, theophylline (TP) oxidation was studied in thermally (TAP) and chemically (CAP) activated persulfate systems, separately and in combination (TCAP). For [TP]₀ = 10 mg L⁻¹, (i) TAP resulted in 60% TP degradation at [PS]₀ = 5 mM and T = 60 °C after 60 min of reaction and (ii) CAP showed slight degradation at room temperature; however, (iii) TCAP resulted in complete TP degradation for [PS]₀ = [Fe²⁺]₀ = 2 mM at T = 60 °C following a pseudo-first order reaction rate with calculated k_obs = 5.6 (±0.4) × 10⁻² min⁻¹. In the TCAP system, the [PS]₀ : [Fe²⁺]₀ ratio of 1 : 1 presented the best results. A positive correlation was obtained between the TP degradation rate and increasing temperature and [PS]₀, and a negative correlation was obtained with increasing pH. Both chloride and humic acid inhibited the degradation process, while nitrates enhanced it. TP dissolved in spring, sea and waste water simulating real effluents showed lower degradation rates than in DI water. Waste water caused the highest inhibition (k_obs = 2.6 (±0.6) × 10⁻⁴ min⁻¹). Finally, the TCAP system was tested on a real factory effluent highly charged with TP, e.g. [TP]₀ = 160 mg L⁻¹, with successful degradation under the conditions of 60 °C and [PS]₀ = [Fe²⁺]₀ = 50 mM.

Chemically activated persulfate in heated medium showed synergistic effect toward full degradation of theophylline in industrial factory effluents. This makes such AOP a well-adapted technology to treat highly concentrated hazardous pharmaceuticals.     

Kinetics and pathways of diclofenac degradation by heat-activated persulfate

In this study, the degradation of diclofenac (DCF) by heat-activated persulfate (HAP) was investigated. It was found that DCF could be degraded efficiently by HAP. The degradation of DCF followed the pseudo-first-order kinetic model, and the highest observed degradation rate constant (k_obs) was obtained at pH 3. The sulfate radical was mainly responsible for DCF removal at pH < 7, whereas it was the hydroxyl radical at high pH. The elimination of DCF was enhanced with the increase in temperature or initial dosage of persulfate. Presence of Cu²⁺ and CO₃²⁻ could improve DCF degradation, while an inhibition effect was observed in the presence of natural organic matter. According to the identified nine transformation products, the potential DCF degradation mechanism was proposed revealing five different reaction pathways, including hydroxylation, decarboxylation, formylation, dehydrogenation and C–N bond cleavage. This study indicates that HAP can effectively oxidize and degrade DCF, especially under acidic conditions.

In this study, the degradation of diclofenac (DCF) by heat-activated persulfate (HAP) was investigated.     

Experimental and theoretical study of CO2 adsorption by activated clay using statistical physics modeling

The objective of this paper was to study CO₂ adsorption on activated clay in the framework of geological storage. The activation of clay was characterized via scanning electron microscopy, N₂ adsorption–desorption isotherms, and X-ray diffraction. The adsorption isotherms were generated at different temperatures, namely, 298 K, 323 K, and 353 K. Based on the experimental result, a new model was simulated and interpreted using a multi-layer model with two interaction energies. The physicochemical parameters that described the CO₂ adsorption process were determined by physical statistical formalism. The characteristic parameters of the CO₂ adsorption isotherm such as the number of carbon dioxide molecules per site (n), the receptor site densities (NM), and the energetic parameters were investigated. In addition, the thermodynamic functions that governed the adsorption process such as the internal energy, entropy, and Gibbs free energy were determined by a statistical physics model. Thus, the results showed that CO₂ adsorption on activated clay was spontaneous and exothermic in nature.

The objective of this paper was to study CO₂ adsorption on activated clay in the framework of geological storage.     

Efficient degradation of organic dyes using peroxymonosulfate activated by magnetic graphene oxide

Magnetic graphene oxide (MGO) was prepared and used as a catalyst to activate peroxymonosulfate (PMS) for degradation of Coomassie brilliant blue G250 (CBB). The effects of operation conditions including MGO dosage, PMS dosage and initial concentration of CBB were studied. CBB removal could reach 99.5% under optimum conditions, and high removals of 98.4–99.9% were also achieved for other organic dyes with varied structures, verifying the high efficiency and wide applicability of the MGO/PMS catalytic system. The effects of environmental factors including solution pH, inorganic ions and water matrices were also investigated. Reusability test showed that CBB removals maintained above 90% in five consecutive runs, indicating the acceptable recyclability of MGO. Based on quenching experiments, solvent exchange (H₂O to D₂O) and in situ open circuit potential (OCP) test, it was found that ˙OH, SO₄˙⁻ and high-valent iron species were responsible for the efficient degradation of CBB in the MGO/PMS system, while the contributions of O₂˙⁻, ¹O₂ and the non-radical electron-transfer pathway were limited. Furthermore, the plausible degradation pathway of CBB was proposed based on density functional theory (DFT) calculations and liquid chromatography-mass spectrometry (LC-MS) results, and toxicity variation in the degradation process was evaluated by computerized structure–activity relationships (SARs) using green algae, daphnia, and fish as indicator species.

Efficient degradation of organic dyes with PMS and magnetic graphene oxide.     

Green and facile edge-oxidation of multi-layer graphene by sodium persulfate activated with ferrous ions

Effective edge oxidation of graphene with high structural integrity is highly desirable yet technically challenging for most practical applications. In this work, we have developed a green and facile strategy to obtain edge-oxidized graphene with good dispersion stability and high electrical conductivity by exploiting high edge reactivity of highly conductive multi-layer graphene and oxidizing radicals (SO₄⁻˙) generated from sodium persulfate (Na₂S₂O₈) with ferrous ion (Fe²⁺) activation. Owing to high structural integrity of pristine graphene and effective edge oxidation, the obtained edge-oxidized graphene exhibited excellent dispersion stability and satisfactory electrical conductivity (i.e. ≥240 S cm⁻¹). Moreover, the oxidation degree of pristine graphene can be well controlled by adjusting treatment time. The obtained edge-oxidized graphene is expected to find a variety of applications in many fields of anti-static films, energy storage materials, flexible sensors and high-performance nanocomposites.

A green and facile strategy is represented to obtain edge-oxidized graphene by exploiting sulfate radicals generated from Na₂S₂O₈ with Fe²⁺ activation.     

Photocatalytic degradation of ethylene by Ga2O3 polymorphs

In this work, we fabricated four different Ga₂O₃ polymorphs, namely, α-, β-, γ-, δ-Ga₂O_3, and investigated their photocatalytic activities by the degradation of ethylene under ultraviolet (UV) light irradiation. Owing to the more positive valence band, all these Ga₂O₃ polymorphs are more photocatalytic reactive than P25 during the degradation of ethylene. The normalized photocatalytic ethylene degradation rate constants of the as-prepared Ga₂O₃ polymorphs follow the order: α-Ga₂O₃ > β-Ga₂O₃ > γ-Ga₂O₃ > δ-Ga₂O₃, which is mainly determined by the position of VBM and the crystallinity of the samples. Among these Ga₂O₃ polymorphs, γ-Ga₂O₃, with the highest surface area, exhibits the highest activity during photocatalytic ethylene degradation, and the degradation rate constant is almost 10 times as that of P25. Furthermore, with the most positive CBM, γ-Ga₂O₃ produces the least CO. These attributes are beneficial for ethylene degradation during post-harvest storage of fruits and vegetables, which makes γ-Ga₂O₃ a potential candidate for practical photocatalytic ethylene degradations.

In this work, we fabricated four different Ga₂O₃ polymorphs, namely, α-, β-, γ-, δ-Ga₂O_3, and investigated their photocatalytic activities by the degradation of ethylene under ultraviolet (UV) light irradiation.     

Degradation of ciprofloxacin by persulfate activated with pyrite: mechanism,acidification and tailwater reuse

Residues of ciprofloxacin (CIP) in the environment pose a threat to human health and ecosystems. This study investigated the degradation of CIP by persulfate (PS) activated with pyrite (FeS₂). Results showed that when [CIP] = 30 μM, [FeS₂] = 2.0 g L⁻¹, and [PS] = 1 mM, the CIP removal rate could reach 94.4% after 60 min, and CIP mineralization rate reached 34.9%. The main free radicals that degrade CIP were SO₄˙⁻ and HO˙, with contributions of 34.4% and 35.7%, respectively. Additionally, compared to the control (ultrapure water), CIP in both tap water and river water was not degraded. However, acidification could eliminate the inhibition of CIP degradation in tap water and river water. Furthermore, acidic tailwater from CIP degradation could be utilized to adjust the pH of untreated CIP, which could greatly promote the degradation of CIP and further reduce disposal costs. The reaction solution was not significantly biotoxic and three degradation pathways of CIP were investigated. Based on the above results and the characterization of FeS₂, the mechanism of CIP degradation in the FeS₂/PS system was that FeS₂ activated PS to generate Fe(iii) and SO₄˙⁻. The sulfide in FeS₂ reduced Fe(iii) to Fe(ii), thus achieving an Fe(iii)/Fe(ii) cycle for CIP degradation.

The efficient degradation of ciprofloxacin in tap and river water was investigated using the FeS₂/PS system and the mechanism was studied. In addition, the tailwater after the reaction could be recycled to further reduce disposal costs.     

A facile heterogeneous system for persulfate activation by CuFe2O4 under LED light irradiation

In this study, the removal performance for rhodamine B (RB) by persulfate (PS) activated by the CuFe₂O₄ catalyst in a heterogeneous catalytic system under LED light irradiation was investigated. The effect of vital experimental factors, including initial solution pH, CuFe₂O₄ dosage, PS concentration, co-existing anion and initial RB concentration on the removal of RB was systematically studied. The removal of RB was in accordance with the pseudo first-order reaction kinetics. Over 96% of 20 mg L⁻¹ RB was removed in 60 min using 0.5 g L⁻¹ CuFe₂O₄ catalyst and 0.2 mM PS at neutral pH. In addition, free radical quenching experiments and electron spin resonance (EPR) experiments were performed, which demonstrated the dominant role of sulfate radical, photogenerated holes and superoxide radical in the CuFe₂O₄/PS/LED system. The morphology and physicochemical properties of the catalyst were characterized by XRD, SEM-EDS, TEM, N₂ adsorption–desorption isotherm, UV-vis DRS, and XPS measurements. Moreover, 18.23% and 38.79% total organic carbon (TOC) removal efficiency was reached in 30 min and 60 min, respectively. The catalyst revealed good performance during the reusability experiments with limited iron and copper leaching. Eventually, the major intermediates in the reaction were detected by GC/MS, and the possible photocatalytic pathway for the degradation of RB in the CuFe₂O₄/PS/LED system was proposed. The results suggest that the CuFe₂O₄/PS/LED system has good application for further wastewater treatment.

In this study, the removal performance for rhodamine B (RB) by persulfate (PS) activated by the CuFe₂O₄ catalyst in a heterogeneous catalytic system under LED light irradiation was investigated.     

白细胞介素2激活的骨髓及脐血单个核细胞体外抗肿瘤活性的…

目的：比较白细胞介素２激活的骨髓及脐血单个核细胞的抗肿瘤活性性，并探讨其其杀伤机制。方法：采用＾３Ｈ－ＴｄＲ前标记释放法和半固体培养等方法研究ＩＬ－２激活的骨髓和脐血的单个核细胞对白血病细胞株ＨＬ－６０细胞Ｋ５６２细胞的抗肿瘤活及ＡＢＭ和ＡＣＢ的造血社细胞活性。     

H2O2-independent chemodynamic therapy initiated from magnetic iron carbide nanoparticle-assisted artemisinin synergy

Chemodynamic therapy (CDT) is a booming technology that utilizes Fenton reagents to kill tumor cells by transforming intracellular H₂O₂ into reactive oxygen species (ROS), but insufficient endogenous H₂O₂ makes it difficult to attain satisfactory antitumor results. In this article, a H₂O₂-free CDT technique with tumor-specificity is developed by using pH-sensitive magnetic iron carbide nanoparticles (PEG/Fe₂C@Fe₃O₄ NPs) to trigger artemisinin (ART) to in situ form ROS. ART-loaded PEG/Fe₂C@Fe₃O₄ NPs are fabricated for the enormous release of Fe²⁺ ions induced by the acidic conditions of the tumor microenvironment after magnetic-assisted tumor enrichment, which results in the rapid degradation of the PEG/Fe₂C@Fe₃O₄ NPs and release of ART once endocytosed into tumor cells. In situ catalysis reaction between the co-released Fe²⁺ ions and ART generates toxic ROS and then induces apoptosis of tumor cells. Both in vitro and in vivo experiments demonstrate that the efficient Fe-enhanced and tumor-specific CDT efficacy for effective tumor inhibition based on ROS generation. This work provides a new direction to improve CDT efficacy based on H₂O₂-independent ROS generation.

Chemodynamic therapy (CDT) is a booming technology that utilizes Fenton reagents to kill tumor cells by transforming intracellular H₂O₂ into reactive oxygen species (ROS), but insufficient endogenous H₂O₂ makes it difficult to attain satisfactory antitumor results.     

Controllable conversion of Prussian blue@yeast bio-template into 3D cage-like magnetic Fe3O4@N-doped carbon absorbent and its cohesive regeneration by persulfate activation

A multitude of heteroatom-doped carbon adsorbents have been explored to cope with ever-growing organic pollution. However, development of these advanced carbon materials with adequate activity and stability remains challenging. Herein, unique 3D cage-like magnetic N-doped Fe₃O₄@C adsorbents were rationally constructed by a one-step pyrolysis of Prussian blue@yeast (PB@yeast) bio-templates. By using yeast as an available biological support, the prepared Fe₃O₄@C hybrids were demonstrated to provide a sufficient number of Fe, N and C atoms for the novel cage-like microstructures, making them a new type of Fe, N co-doped carbon absorbents with a facile preparation procedure and remarkable adsorption behavior. Rhodamine B (RhB) removal indicated that the prepared N-doped Fe₃O₄@C adsorbents displayed high adsorption capabilities in a near-neutral solution, and Fe₃O₄@C (1 : 0.11) exhibited a maximum adsorption capability of 257.06 mg g⁻¹. More importantly, spent N-doped Fe₃O₄@C absorbents, which could be recovered by magnetic separation and cohesive persulfate (PS) activated photo-Fenton regeneration, showed excellent adsorption reusability and high stability even after 5 cycles. Overall, this paper presents a simple method for fabrication of a 3D cage-like magnetic N-doped Fe₃O₄@C adsorbent, which provides a significant guidance for the study of Fe, N co-doped carbon adsorbents towards dye wastewater treatment.

Fe/N co-doped carbon adsorbents have been explored to cope with ever-growing organic pollution.     

Enhanced heterogeneous Fenton-like degradation of methylene blue by reduced CuFe2O4

To facilitate rapid dye removal in oxidation processes, copper ferrite (CuFe₂O₄) was isothermally reduced in a H₂ flow and used as a magnetically separable catalyst for activation of hydrogen peroxide (H₂O₂). The physicochemical properties of the reduced CuFe₂O₄ were characterized with several techniques, including transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and magnetometry. In the catalytic experiments, reduced CuFe₂O₄ showed superior catalytic activity compared to raw CuFe₂O₄ for the removal of methylene blue (MB) due to its relatively high surface area and loading Fe⁰/Cu⁰ bimetallic particles. A limited amount of metal ions leached from the reduced CuFe₂O₄ and these leached ions could act as homogeneous Fenton catalysts in MB degradation. The effects of experimental parameters such as pH, catalyst dosage and H₂O₂ concentration were investigated. Free radical inhibition experiments and electron spin resonance (ESR) spectroscopy revealed that the main reactive species was hydroxyl radical (˙OH). Moreover, reduced CuFe₂O₄ could be easily separated by using an external magnet after the reaction and remained good activity after being recycled five times, demonstrating its promising long-term application in the treatment of dye wastewater.

CuFe₂O₄ was reduced for activation of hydrogen peroxide and the reduced CuFe₂O₄ showed a relatively higher catalytic activity.     

Photocatalytic dye degradation and biological activities of the Fe2O3/Cu2O nanocomposite

The present study reports the synthesis of the Fe₂O₃/Cu₂O nanocomposite via a facile hydrothermal route. The products were characterized using X-ray diffractometry (XRD), Fourier-transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), high-resolution transmission electron microscopy (HR-TEM), energy dispersive spectroscopy (EDS) and Brunauer–Emmett–Teller (BET) techniques. The composition, morphology and structural features of the nanoparticles were found to be size-dependent due to the temperature response in the particular time log during hydrothermal synthesis. HR-TEM confirmed the formation of hexagonal rod-shaped bare Cu₂O, rhombohedral-shaped Fe₂O₃ and composite assembly. Rhodamine-B (RB) and Janus green (JG) were chosen as model dyes for the degradation studies. Photocatalytic degradation of the dyes was deliberated by altering the catalyst and dye concentrations. The results showed that the Rhodamine-B (RB) and Janus green (JG) dyes were degraded within a short time span. The synthesized materials were found to be highly stable in the visible light-driven degradation of the dyes; showed antibacterial activity against E. coli, P. aeruginosa, Staph. aureus and B. subtilis; and exhibited less toxicity against the Musmusculus skin melanoma cells (B16-F10). The fusion of these advantages paves the way for further applications in energy conversion, biological applications as well as in environmental remediation.

The present study reports the synthesis of the Fe₂O₃/Cu₂O nanocomposite via a facile hydrothermal route.